Despite an extensive literature evaluating the chronic effects of exposure to solvent mixtures, solvent 'encephalopathy remains controversial. Although plagued by inadequate characterization of exposure and control of confounding variables, this literature suggests that working memory, which relies on frontal brain structures, is the cognitive function most sensitive to chronic solvent exposure. Construction painters are among those workers most highly exposed to mixtures of organic solvents. The purpose of the present study is to compare cognitive performance and neural activation between construction painters with more than 10 years on the job to drywaller/tapers with minimal exposure to neurotoxicants but matched on demographic and work history profiles. In cooperation with the International Union of Painters and Allied Trades, 150 construction painters (exposed) and 150 drywaller/tapers (controls) will complete a physical examination, visual contrast sensitivity, screening tests of cognitive function (Le., symbol digit substitution (SDS), reaction time, finger tapping), and the Cambridge Neuropsychological Test Automated Battery (CANTAB) to assess attention, working and visual memory. Two subsets of exposed and their matched controls (25 "impaired" exposed: SDS 2: 1.5 standard deviations below estimated intelligence; 25 "unimpaired" exposed) will be scanned using Blood Oxygen Level Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) while completing tests of working memory to determine neural activation. A second purpose will be to !calculate distributions of exposure for each subject using Monte Carlo techniques for both inhalation and dermal exposures based on painting techniques, current and past paint materials composition along with use of protective equipment. These exposure estimates will be modified by variables known to affect dose and susceptibility including current and past body mass index (BMI), lifetime alcohol ingestion, and genetic polymorphisms associated with variability in solvent metabolism.